Method for manufacturing thin semiconductor chip

ABSTRACT

In manufacturing a thin semiconductor chip, a wafer is stably held during processing to maintain a stable shape and to avoid generation of cracks on the wafer. When a thin wafer having a surface thereon is to be processed, a rigid support body is adhered to the other surface of the thin wafer and a ring-shaped frame, encircling an outer periphery of the thin wafer, is adhered to the rigid support body.

TECHNICAL FIELD

The present invention relates to a method for manufacturing a thinsemiconductor chip in which a thin wafer is divided, into individualsemiconductor chips, after one of the surfaces of the thin wafer isprocessed. The method for manufacturing a thin semiconductor chipaccording to the present invention can be used, for example, when alaser element is formed on a thin substrate of gallium arsenic or a thinsubstrate of sapphire.

BACKGROUND OF ART

In the prior art, it has been very difficult to process a thin wafer,having a thickness of 100 μm or less, to form a pattern on the surfaceof the wafer, to form a film by sputtering or other process, to etchthereon, or to divide the wafer into individual pieces of chips. Thereasons are that it has been difficult to stably hold the wafer duringthese processes, while maintaining the shape and this causes cracks onthe wafer and a lack of uniform production due to the deformation of thewafer.

DISCLOSURE OF INVENTION

The present invention was made to overcome the above-mentioned problemsand, therefore, the object of the present invention is to provide amethod for manufacturing a thin semiconductor chip in which, when thethin wafer is processed, the wafer can be stably held during variousprocesses so as to maintain a stable shape and so that cracks on thewafer and a lack of uniform production, due to the deformation of thewafer, can be avoided.

In order to achieve the above-mentioned object, according to the presentinvention, there is provided a method of manufacturing a thinsemiconductor chip from a thin wafer, having one of the surfaces thereofprocessed, the method comprising: adhering a rigid support body to theother surface of the thin wafer and adhering a ring-shaped frame,encircling an outer periphery of the thin wafer, to the rigid supportbody.

A double-side adhesive tape is used to adhere the rigid support body,the thin wafer and the ring-shaped-frame.

According to another aspect of the present invention there is provided amethod of manufacturing a thin semiconductor chip, the methodcomprising: adhering a protective tape to a circuit forming surface of athin wafer; adhering the thin wafer, at a surface opposite to thecircuit forming surface thereof, to a dicing tape and adhering aring-shaped frame encircling the outer periphery of the thin wafer tothe dicing tape; peeling the protective tape off; dicing the thin waferfrom a side of the circuit forming surface thereof to divide the thinwafer into a plurality of pieces of individual thin chips; and pickingup the individual thin chips.

According to still another aspect of the present invention there isprovided a method of manufacturing a thin semiconductor chip, the methodcomprising: a. adhering a protective tape to a circuit forming surfaceof a thin wafer; b. adhering the thin wafer at a side of the protectivetape to a first tape and adhering a first ring-shaped frame encirclingan outer periphery of the thin wafer to the first tape; c. forming aback electrode on a surface of the thin wafer opposite to the circuitforming surface; d. forming a resist pattern on the back electrode; e.etching along the resist pattern to divide the back electrode and thethin safer into individual thin chips; f. removing the resist pattern;g. adhering the thin wafer at a side of the back electrode thereof to asecond tape and adhering a second ring-shaped frame encircling an outerperiphery of the first ring-shaped frame to the second tape; h.irradiating ultraviolet light onto a side of the first tape in such amanner that an adhesive force, between the protective tape and the thinchips, is reduced to separate the protective tape, the first tape andthe first ring-shaped frame from the thin wafer; and i. picking up theindividual thin chips.

According to a further aspect of the present invention there is provideda method of manufacturing a thin semiconductor chip, the methodcomprising: a. adhering a protective tape to a circuit forming surfaceof a thin wafer; b. adhering the thin wafer at a side opposite to theprotective tape to a first tape and adhering a second ring-shaped frame,encircling an outer periphery of the thin wafer with a gap, to the firsttape; c. peeling the protective tape off; d. adhering a firstring-shaped frame, encircling an outer periphery of the thin wafer andbeing accommodated in an inner periphery of the second ring-shapedframe, to the first tape and adhering a second tape to the circuitforming surface of the thin wafer and to the first ring-shaped frame; e.removing the first tape and the second ring-shaped frame from the thinwafer and, then, forming a back electrode on a surface of the thin waferopposite to the circuit forming surface; f. forming a resist pattern onthe back electrode; g. etching along the resist pattern to divide theback electrode and the thin wafer into individual thin chips; h.removing the resist pattern; i. adhering the thin wafer at a side of theback electrode thereof to a second tape and adhering a secondring-shaped frame encircling an outer periphery of the first ring-shapedframe to the second tape; j. irradiating ultraviolet light onto a sideof the first tape in such a manner that an adhesive force between theprotective tape and the thin chips is reduced to separate the protectivetape, the first tape and the first ring-shaped frame from the thinwafer; and k. picking up the individual thin chips.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1(A) to 1( c) show a first embodiment of a method formanufacturing a thin semiconductor chip of this invention;

FIGS. 2(A) and 2(B) show a second embodiment of a method formanufacturing a thin semiconductor chip of this invention;

FIGS. 3(A) to 3(E) show a third embodiment of a method for manufacturinga thin semiconductor chip of this invention;

FIGS. 4(A) to 4(J) show a fourth embodiment of a method formanufacturing a thin semiconductor chip of this invention; and

FIGS. 5(A) to 5(E) show a fifth embodiment of a method for manufacturinga thin semiconductor chip of this invention;

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will now be described in detailwith reference to the drawings.

FIGS. 1(A) to 1( c) show a first embodiment of a method formanufacturing a thin semiconductor chip of this invention. A wafer 1 isof a thin disk-like configuration having a diameter (D1) of 6 inches(150 mm) and a thickness (t) of approximately 100 μm. One of thesurfaces of the wafer 1 is a circuit forming surface 1 a. To more easilyhandle the wafer 1, a tape 2 and a ring-shaped frame 3 having relativelystrong base are used. One of the surfaces of the tape 2 is an adhesivesurface 2 a.

FIG. 1(A) shows a type A, in which a ring-shaped frame 3 having an innerdiameter larger than the outer diameter of the wafer 1 is used. Theupper surface 1 a of wafer in FIG. 1 is a circuit forming surface andthe opposite surface 1 b is adhered to the adhesive surface 2 a of thetape 2. The ring-shaped frame 3 is adhered to the adhesive surface 2 aof the tape 2 and encircles the outer periphery of the wafer 1. A gap 4is defined between the outer diameter of the wafer 1 and the innerdiameter of the ring-shaped frame 3. The height (d) of the ring-shapedframe 3 is larger than the thickness (t) of the wafer 1.

FIG. 1(B) shows a type B, in which the difference between the outerdiameter of the wafer 1 and the inner diameter of the ring-shaped frame3 is 2 mm or less (the gap 4 therebetween is 1 mm or less). In the samemanner as type A, the height (d) of the ring-shaped frame 3 is largerthan the thickness (t) of the wafer 1. In the same manner as type A, thesurface 1 b of the wafer 1 opposite to the circuit forming surface 1 ais adhered to the adhesive surface 2 a of the tape 2 and the ring-shapedframe 3 is adhered to the adhesive surface 2 a of the tape 2 andencircles the periphery of the wafer 1. In this case, a very small gap 4is defined between the outer diameter of the wafer 1 and the innerdiameter of the ring-shaped frame 3.

FIG. 1(C) shows a type C, in which the difference between the outerdiameter of the wafer 1 and the inner diameter of the ring-shaped frame3 is 2 mm or less (the gap 4 therebetween is 1 mm or less), in the samemanner as type B. The height (d) of the ring-shaped frame 3 issubstantially same as the thickness (t) of the wafer 1. In the samemanner as types A and B, the surface 1 b of the wafer 1 opposite to thecircuit forming surface 1 a is adhered to the adhesive surface 2 a ofthe tape 2 and the ring-shaped frame 3 is adhered to the adhesivesurface 2 a of the tape 2 and encircles the outer periphery of the wafer1. In this case, a very small gap 4″ is defined between the outerdiameter of the wafer 1 and the inner diameter of the ring-shaped frame3 and the thickness (t) of the wafer 1 is the same as the height (d) ofthe ring-shaped frame 3.

FIGS. 2(A) and 2(B) show a second embodiment of a method formanufacturing a thin semiconductor chip of this invention. In thisembodiment, a double-face adhesive tape 6 is adhered to a rigid body 5and the surface 1 b of the wafer opposite to the circuit forming surface1 a is adhered to the double-face adhesive tape 6. In addition, aring-shaped frame 3 is adhered to the double-face adhesive tape 6 andencircles the outer periphery of the wafer 1. The wafer 1 itself is thesame as that used in the previous embodiments.

FIG. 2(A) shows a case in which the height (d) of the ring-shaped frame3 is larger than the thickness (t) of the wafer 1 and FIG. 2(B) shows acase in which the height (d) of the ring-shaped frame 3 is substantiallythe same as the thickness (t) of the wafer 1.

A rigid body 5 may be a glass, particularly a silica glass, a wafer, ametal, a polymer or the other, which can be selected in relation to amethod for peeling it from the double-face adhesive tape 6. Thedouble-face adhesive tape 6 can be selected as one which can be peeledoff by irradiating ultraviolet light or can be thermally peeled off. Itis advantageous that the double-face adhesive tape 6 is selected fromone which can be easily peeled off the rigid body 5 but is highlyadhesive to the ring-shaped frame 3.

In these embodiments, the lower surface of the wafer 1 is supported bythe rigid body 5 and, therefore, it can easily be applied to a spinner.In addition, as the ring-shaped frame 3 exists, the double-face adhesivetape 6 can be easily peeled off.

FIGS. 3(A) to 3(E) illustrate respective steps A to E in a thirdembodiment of a method for manufacturing a thin semiconductor chip ofthis invention. In a step (A), a protective tape 7 is adhered to acircuit forming surface 1 a of the thin wafer 1.

Next, in step (B), a dicing tape 8 is adhered to a surface 1 b of thethin wafer 1 opposite to the circuit forming surface 1 a. Thering-shaped frame 3 is adhered to the dicing tape 8 and encircles theouter periphery of the wafer 1. Although, in general, the dicing tape 8is usually adhered after the protective tape 7 is peeled off, in thisembodiment, after the wafer 1 is held by the dicing tape 8, theprotective tape 7 is peeled off. Therefore, it is advantageous that thewafer will rarely be damaged.

Next, in step (C), the protective tape 7 is peeled off. Then in step(D), the thin safer 1 is diced from the side of the circuit formingsurface 1 a, in such a manner that the thin wafer 1 is divided intoindividual pieces of semiconductor chips 10. The size of the dividedpieces depends upon the particular purpose of the semiconductor chip 10;in general, a desired rectangular-shaped thin chip 10 is obtained bydicing the wafer both in longitudinal and lateral directions. Next, instep (E), the individual pieces of thin chip are picked up.

According to the embodiment shown in FIGS. 3(A) to 3(E), although ageneration of cracks on the wafer 1 can be reduced, there are somedrawbacks, i.e., processing from the back surface of the wafer, forexample, electrode forming, patterning or etching cannot be done.

To solve these problems, the embodiments shown in FIGS. 4 and 5 canadvantageously be used.

FIGS. 4(A) to 4(J) relate to a fourth embodiment of the presentinvention and show the respective steps A to J of a method formanufacturing a thin semiconductor chip using two kinds of ring-shapedframes. First, in step (A), a protective tape 7 is adhered to thecircuit forming surface 1 a of the thin wafer 1. Next, in step (B), thethin wafer 1 at the side of the protective tape 7 is adhered to a firsttape 11. On the other hand, a first ring-shaped frame 3 is adhered tothe first tape 11 to encircle the outer periphery of the thin wafer 1.

Next, in step (C), a back electrode 12 is formed on a surface 1 b of thethin wafer 1, opposite to the circuit forming surface 1 a. The materialof the back electrode 12 is Al, Cu, Au or other, formed over the entiresurface of the thin wafer 1 and the first ring-shaped frame 3. The backelectrode 12 can be formed by sputtering or vapor deposition of a metal,after the surface of the thin wafer 1 opposite to the circuit formingsurface 1 a is rinsed. Next, in step (D), a resist pattern 13 is formedon the back electrode 12. Next, in step (E), the back electrode 12 isetched along the resist pattern 13 and, in step (F), a layer of the thinwafer 1 is divided by etching into individual pieces of thin chips 10.

Next, in step (G), the resist 13 is removed by an ashing process. Next,in step (H), a second tape 14 is adhered to the thin wafer 1 at the sideof back electrode 12. A second, outer ring-shaped frame 15 encirclingthe outer periphery of the first, inner ring-shaped frame 3 is alreadyadhered to this second tape 14. Next, in step (I), ultraviolet light isirradiated from the side of the first tape 11 to weaken the adhesiveforce between the protective tape 7 and the thin chip 10 to separate theprotective tape 7, the first tape 11 and the first, inner ring-shapedframe 3 from the thin wafer 1. Next, in step (J), the individual thinchips 10 are picked up to obtain separate individual chips 10.

In the embodiment shown in FIGS. 4(A) to 4(J), if the individual thinchips 10 are directly picked up in the step (G), the circuit formingsurface of the thin chip 10 might be damaged when separating it from theprotective tape 7. Therefore, the above-mentioned method should adopted.Otherwise, if a pick-up method which involves no such problems can beadopted, it is possible to omit step (H) and subsequent steps, after theindividual thin chips 10 are picked up in step (G).

FIGS. 5(A) to 5(E) show a fifth embodiment of this invention, i.e., amethod for manufacturing a thin semiconductor chip in which theprotective tape is peeled off before the support body is adhered. First,in step (A), a protective tape 7 is adhered to the circuit formingsurface 1 a of the thin wafer 1. Next, in step (B), the thin wafer 1 atthe surface thereof opposite to the surface thereof on which theprotective tape 7 is adhered, is adhered to a first tape 11. An outer,ring-shaped frame 15, encircling the outer periphery of the thin wafer 1with a gap therebetween, is already adhered to this first tape 11. Next,in step (C), the protective tape 7 is peeled off. Next, in step (D), aninner ring-shaped frame 3, encircling the outer periphery of the thinwafer 1 and accommodated within the inner periphery of the outerring-shaped frame 15, is adhered to the first tape 11 and a second tape16, which is abutted to the inner ring-shaped frame 3, is adhered to thecircuit forming surface 1 a of the thin wafer 1. In this embodiment, theouter and inner ring-shaped frame 15 and 13 are in the same spatialrelationship but are processed in the reverse order relatively to thosesame frames 15 and 13 in the fourth embodiment. Next, in step (E), thefirst tape 11 and the outer ring-shaped frame 15 are removed. As thesubsequent steps in this embodiment, the step (C) in FIG. 4C and thesubsequent steps thereof can be adopted. In this embodiment, if thereare no problems in directly picking up the thin chips 10, the step (H)and the subsequent steps thereof in FIG. 4 can be omitted.

It should be understood by those skilled in the art that the foregoingdescription relates to only preferred embodiments of the disclosedinvention, and that various embodiments, changes and modifications maybe made to the invention without departing the sprit and scope thereof.The present invention can be applied to various size of wafer, such asan 8-inch wafer or a 6-inch wafer.

As described above, according to the present invention, when a thinwafer is processed, the wafer can be maintained in a stable state duringvarious steps so that cracks or deformation in the thin wafer and a goodproductivity of thin semiconductor chips can be obtained and, also, theproduction efficiency can be improved.

1. A method of manufacturing a thin semiconductor chip, comprising:adhering a protective tape to a circuit forming surface of a thin wafer;adhering said protective tape, and thereby said thin wafer, to a firsttape and adhering an inner ring-shaped frame, encircling an outerperiphery of the thin wafer, to said first tape; forming a backelectrode on a surface of the thin wafer opposite to the circuit formingsurface; forming a resist pattern on said back electrode; etching alongsaid resist pattern to divide said back electrode and said thin waferinto individual thin chips; removing said resist pattern; adhering saidindividual thin chips to a second tape and adhering an outer ring-shapedframe, encircling an outer periphery of the first ring-shaped frame, tosaid second tape; irradiating ultraviolet light onto a side of saidfirst tape thereby to reduce an adhesive force between said protectivetape and said thin chips and facilitate separating said protective tape,said first tape and said inner ring-shaped frame from said thin chips;and picking up said individual thin chips.
 2. A method of manufacturinga thin semiconductor chip, said method comprising: adhering a protectivetape to a circuit forming surface of a thin wafer; adhering said thinwafer at a surface thereof, opposite to the circuit forming surfacethereof adhered to the protective tape, to a first tape and adhering afirst outer ring-shaped frame, encircling an outer periphery of the thinwafer with a gap therebetween, to said first tape; peeling saidprotective tape off the circuit forming surface; adhering an innerring-shaped frame, encircling an outer periphery of the thin wafer andaccommodated within an inner periphery of the first outer ring-shapedframe, to said first tape and adhering a second tape to the circuitforming surface of the thin wafer and to said inner ring-shaped frame;removing said first tape and said outer ring-shaped frame from the thinwafer and, then, forming a back electrode on a surface of the thin waferopposite to the circuit forming surface thereof; forming a resistpattern on said back electrode; etching along said resist pattern todivide said back electrode and said thin wafer into individual thinchips; removing said resist pattern; adhering said individual thin chipsto a third tape and adhering an outer ring-shaped frame, encircling anouter periphery of the inner ring-shaped frame, to said third tape;irradiating ultraviolet light onto a side of said second tape thereby toreduce an adhesive force between said second tape and individual saidthin chips separate and facilitate separating said second tape and saidinner ring-shaped frame from said individual thin chips; and picking upsaid individual thin chips.